1. Field of the Invention
The present invention relates to a semiconductor device having through plugs, more particularly, to a semiconductor device in which highly reliable through plugs are formed with good productivity.
2. Description of the Related Art
In accordance with the reduction in size and weight of electronic equipment such as portable devices and mobile devices, downsizing and higher-density design are being demanded also for electronic components constituting the electronic equipment. As one of such electronic components, used is a stacked-type semiconductor device (multichip device) in which semiconductor integrated circuit chips (LSI chips) are three-dimensionally stacked.
Among multichip devices, a structure with the highest integration degree and thus allowing downsizing is such a type of multichip device having a three-dimensionally stacked structure in which through plugs are formed through semiconductor substrates having semiconductor devices formed thereon. In this type of device, the through plugs electrically connecting a face of the semiconductor substrate in which elements are formed to a rear face side are formed. The through plug is constituted of an insulating material covering a sidewall of a through hole and a low electrical resistance metal material (for example, Al, Cu, or the like) in a columnar shape that is positioned so as to be surrounded by the insulating material and that serves as a conductive member. The low resistance of the conductive member ensures the operating performance as a system.
Here, it is more advantageous in view of processes that a through plug forming step is carried out after the completion of a transistor forming step called a frontend process which requires a relatively high-temperature process, in other words, during a multilayer interconnection forming step that is a backend process. Usable methods of forming through holes in which the through plugs are to be formed are reactive ion etching (RIE) using plasma, which is anisotropic etching, and wet etching using an etchant of an alkali solution.
An example of a semiconductor device fabrication method including a through hole forming step is a method described in a patent document: Japanese Patent Laid-open Application No. Hei 10-223833.